Honda XR 400R

The new XR400 four stroke is, according to Honda, the future of dirt bikes. While we didn't have a chance to compete on the XR 400 we did subject the machine to a wide variety of conditions, some of which you probably already ride in or are likely to encounter. This included many, many laps at two motocross tracks native to Southern California - Perris Raceway, and Starwest.

We threw in some high speed desert riding, a splash of medium speed trail riding and some tight, rocky technical stuff just for fun. Winter is Southern California's rainy season, and prime dirt riding time; for the most part the soil was fairly moist, providing for good traction all around.

The XR's new kickstart mechanism features taller gearing and an automatic decompression system. This combined with a completely re-mapped CDI results in an open class engine that requires surprisingly little effort to start. Wth the choke on and no throttle, a couple of smooth consistent kicks is all. The engine warms up briskly and can be ridden full on in just a few minutes. The XR is also fitted with a manual decompression lever for quickly clearing the cylinders of excess gas after a getoff.

Power delivery is strong and smooth right off the line and through the midrange, and the lone 36mm Keihin does a fine job of aspirating the 397cc engine well into the upper rpm's. Peak power is reached at 7,500 rpm after which the eager motor politely begs to be shifted. Ample mid-range torque is available, making wheelies on the XR easy. Honda credits the XR's wide range of power to a design concept they've been utilizing for over ten years.

The Radial Four Valve Combustion chamber (RFVC) allows for the use of large valves, better flow and a unique valve actuating method. Due to the positioning of the sub-rocker arm, the rocker arm and valve operate on different planes, and the entire valve train should theoretically last longer.

"Clutch action is smooth and strong with no evidence of slippage."

The XR borrows its clutch cover design from the easily-removable CR-type making replacement a snap. Shifting is light and precise both on the way up and back down, under load, and while engaged in high speed coasting. Honda attributes the transmission's friendly disposition to a re-designed gear shift cam, a specially polished shift fork guide, and an improved countershaft spline design.

We did, however, experience some resistance to shifting after the gearbox heated up. While the problem never occurred during high speed riding, or even while engaging in full-spirited trail riding, the XR simply refused to shift above 3rd gear on the motocross track. The problem only popped up when the bike was heavily flogged. We suspect a bent shifting fork but, hey, test bikes live hard lives.

Despite temperature related transmission troubles the engine never experienced overheating or noticeable loss of power during our entire test. We were a bit surprised to see an air-cooled motor still being offered, especially on a motorcycle that is being touted by Honda as a competition machine. But air is always available, and it's cheap and doesn't weigh anything. In fact the lack of water cooling combined with a dry sump lubrication system keeps the engine weight down to a mere 84.2 lbs. That's just 10ounds more than the XR250R powerplant. Oil is forced through the system while large cooling fins on the motor, and a futuristic looking oil cooler living under the headlight, are the departure points for heat.

The brush guards will serve you just fine for riding in brush and keeping bugs from splatting on your nice clean gloves. Toss them in favor of an aftermarket set of hand guards if you really like your fingers. The combination headlight/numberplate design is first rate; the multi-piece assembly quickly detaches when you don't need it. And since it's two separate components, the likelihood of having to replace both in a crash is reduced. For those of you who are nutty enough to want to ride at night, Honda offers an optional 55W bulb over the stock 35W.

Stopping the thumper are the same high quality Nissan units used on the CR motocrossers. There is no shortage of braking power here. Action is light and resistant to fade at both ends. Our rear brake took a vacation only once when the wheel became submerged in a goopy mess of mud. Once rolling again, a few taps on the pedal is all it took to bring things back to normal.

Suspending the XR up front is a fat 43mm catridge fork with 11 inches of front wheel travel. Honda claims the unit is very similar in construction to the fork design used on their CBR900RR street bike. With 18-position compression damping and 12-position rebound damping, the forks can be set up for a variety of situations. Neatly tucked under the seat are the "brains" of the rear suspension. A Showa shock featuring standard spring preload adjustment, as well as 16 position compression and rebound damping adjustability, offers 11.8 inches of rear wheel travel.

Preaching the religion of short wheelbases, the XR400 spans 56.1 inches, just one inch longer than the new XR250R, and .20 inches shorter than the original XR350. Fork rake is 25 degrees 15 minutes (XR250R is 24 degrees 54 minutes), with a trail of 94mm, (XR250R is 92mm). The XR350 of yesteryear had 116mm of trail.

The XR shined in sand washes and fast one-track roads. Subtle bumps and well groomed jumps were not a problem. The Honda torqued its way through the rocks and loose gravel without a hitch. On the motocross track the XR held its own - if only we could've held on. Severe drop-offs were more of a challenge and, while the bike never bottomed out, we were wishing we hadn't visited the all-you-can-eat breakfast buffet that morning.

Details

Bodywork is sleek, easy to remove, and of high quality. All controls are well laid out. Overall the ergonomics of the bike feel pretty good. The seat is comfy and slim, as is the tank. We would opt for a bit less padding if asked. The engine's counterbalancing system does a great job of reducing vibration to the handlebars, thereby reducing potential rider fatigue. The exhaust system is all new, featuring a spark arrestor and removable baffle.

We ran our XR with the baffle and airbox restrictor removed. The new combination of chassis and suspension are pure bliss resulting in a bike that turns relatively quick, yet can tackle the straight stuff with confidence. Very aggressive riders will want to go through the regular routine of swapping springs and revalving, but they'll be starting with a terrific platform that suits the masses and then some. Box stock, the Honda is the closest you're going to get to a race ready 4-stroke for the price.

Source Motorcycle.com